Let the radius of the semicircular grass plot be r
Now, Perimeter of a semicircular grassy = Circumference of semicircular grassy plot + diameter of semicircular grassy plot
⇒72=12(2πr)+2r⇒72=227r+2r⇒72=36r7⇒r=14 m
Now, the distance(R) of the circumference of the path from the centre is given by
14 + 3.5 = 17.5 m
Now, Area of path is given by
=12πR2−12πr2=12×227×17.5×17.5−12×227×14×14=481.25 −308=173.25 m2
=12(2πr)+d=πr+d=πd2+d=227×7+14=22+14=36 cm
Hence, the perimeter of a semicircular protractor is 173.25 m2